Process for the production of unsaturated nitriles



United States Patent 3,321,507 PROCESS FOR THE PRODUCTIQN 0F UNSATURATEDNITRELES Alessandro Ginnasi, Milan, Marcello Massi Maori, San DonateMilanese, and Antonio Colombi, Milan, Italy, assignors to SNAM S.p.A.,Milan, Italy, a company of Italy No Drawing. Filed Mar. 31, 1964, Ser.No. 356,045 Claims priority, application Italy, Apr. 1, 1963, 6,603/63,Patent 690,486 Claims. (Cl. 260-4653) It is an object of the presentinvention to provide a process of the preparation of unsaturatednitriles. More particularly the invention relates to the preparation ofacrylonitrile from olefins, ammonia and oxygen, operating in thepresence of catalysts.

The so-called ammoxydation reaction has been known for a long time,which takes place when an olefin is reacted in the gaseous phase, withoxygen or ammonia in the presence of suitable catalysts, obtainingnitrogen compounds which in suitable conditions are prevailinglyunsaturated nitriles. Acrylonitrile is obtained by ammoxydation ofpropylene. As catalysts the literature indicates a vast range of metalsfrom the End to the VIIth group of the periodic system or theircompounds, for instance oxides or mixtures thereof. The known processeshave not revealed so far the possibility of obtaining acrylonitrilestarting from olefinic mixtures containing both propylene and butylenes,which however would be very convenient and advantageous.

It has now been found-and this forms the subject matter of the presentinventionthat it is possible to obtain in a convenient and advantageousmanner acrylonitrile while starting from hydrocarbon mixtures containingpropylene as well as butylene. Such a process represents a considerabletechnical progress in that it makes possible conversion of propyleneinto acrylonitrile Without any or at any rate with only minimalcracking, whilst the contemporaneous conversion of the C insteadrequires that these be cracked in a controlled manner, in order toprovide said unsaturated nitrile while excluding other nitrilesundesirable for subsequent purifying operations.

It is apparent that the realization of a process wherein a component ofthe olefinic feed is not cracked, while the other components are crackedin a controlled manner, so that the C and C olefins all contribute tothe acrylonitrile yield, constitutes an unexpected and surprising resultnot only with respect to the explicit teachings of the art, but alsowith respect to the expectations that could and had to be made intheory. In the process of the present invention hydrocarbon m'mturescontaining propylene and butylenes are reacted in the gaseous phase,with oxygen and ammonia, in the presence of catalysts comprisingmolybdenum, vanadium and bismuth, wherein the active part contains from0.5 to 3% by weight, and preferably from 1.3 to 1.8% of vanadium.

In a preferred embodiment of the invention, one operates with mixturesof olefins, oxygen, ammonia, in which the olefins are overall (C +C.,)in molar quantities smaller with respect to oxygen, and about equal orsmaller with respect to ammonia.

The active part of the catalysts employed, which are convenientlysupported, may be mixtures of oxides of molybdenum, vanadium andbismuth, or be other compounds or mixtures of compounds, in particular,the product of the calcination of a bismuth salt of a heteropolyacid ofvanadium or molybdenum.

The ammonia-to-olefins ratio is not strictly critical. It is necessaryat any rate that the ammonia should be fed at least in stoichiometricratio to the overall quantity of olefins. There are no upper limits, ifnot dictated by economical factors since the excess ammonia is hardlyrecoverable. An upper practical limit can be indicated in the molarratio NH /olefins=l.2. The oxygen should be fed in ratios to saidoverall quantity of olefins higher than 1 and preferably not higher than2. It is advantageous that the oxygen should be fed with convenientdiluents, such as nitrogen or carbon dioxide. In particular it isconvenient to feed air.

It is preferable to conduct the reaction in the gaseous phase, in thepresence of water, which can be fed in molar ratios even many timesgreater than 1, to the overall quantity of olefins such as for instanceup to 20 moles of water per mole of olefins.

The time of contact is not critical, showing an optimum for durationsshorter than 30 and preferably shorter than 10 seconds and equal atleast to 0.5 second. The presence of saturated hydrocarbons in the feeddoes not cause any inconveniences.

The catalyst is generally supported on kieselguhr, celite orcarborundum. In this case it can be prepared by mixing the active partwith a support, kneading and then drying the whole. The solid massobtained is ground to a convenient grain size and is then tablettedafter previous addition of a suitable substance having the func tion ofa binder.

The tabletted catalyst is charged into the reactor and is activated insitu by oxygen or air at 480 to 540 C., the optimum being shiftedtowards the temperatures closest to the upper limit.

A further advantage of the present invention is the absence of anydanger in connection with the production of acrylonitrile, since noformation of acrolein has been noticed, the mixtures of which with airare notoriously explosive, or at any rate the formation of this aldehydehas always been below the explosive limits. It is obvious that it ispossible to convert into nitriles, in the manner described in thepresent patent application, not only the mixtures of olefins but alsothe individual olefins that normally form part of the mixtures.

The invention will be more fully understood from the followingnon-limiting working examples.

EXAMPLE 1 2700 g. of Bi(NO -5H O, 1200 g. of ammonium molybdate and 70g. of ammonium metavanadate, are calcined separately in a mufile at 450to 500 C. and then mixed. A catalyst is obtained consisting of a mixtureof oxides of vanadium, molybdenum and bismuth.

The active part so obtained is mixed with 1 kg. of celite, kneaded withwater, extruded and reduced into pellets. The catalyst so prepared ischarged, after drying, into the reactor constituted by a steel tube, andis activated in situ with air for 8 hours at 500 C.

If there is fed into the reactor, kept at 510 C., apropylene-ammonia-air-water mixture, respectively in molar ratios1/1/7.5/15, at a space-velocity of 950 Nl./l. (of catalyst) hr., onegets a conversion into acrylonitnle of 54.2%, into acetonitrile of 3.5%,and into hydrocyanic acid of 8.5%, with a yield of useful products equalto 82%.

EXAMPLE 2 2700 g. of Bi(NO -5H O are dissolved in 300 ml, of nitric aciddiluted with one liter of water. Another solution is prepared apart bydissolving 1200 g. of ammonium molybdate (81% of M00 and 70 g. ofmetavanadate of ammonium in 1 liter of water saturated with ammonia,then diluting the Whole with 1500 ml. of water. After having heated thetwo solutions up to C., the second solution is added to the first one,keeping the whole under stirring. A sludgy paste of brown colour isobtained which when cooled and washed with water and dried, shows onanalysis the following results:

Percent by weight The remainder is oxygen.

The analysis of this product by X-rays shows the band of one singlecompound, the composition of which corresponds to a bismuth salt of aheteropolyacid of vanadium or molybdenum.

The active part so obtained is mixed with 1 kg. of kieselguhr and withwater: the paste so prepared is extruded and reduced into pellets. Theseare dried and calcined in a muflle at 450 to 500 C. for 12 hours. Oneliter of the catalyst so prepared is charged into the same synthesisreactor of Example 1 and then activated by a stream of oxygen at 510 C.for 8 hours.

There is then fed to the reactor, kept at 510 C., apropylene-ammonia-air-water mixture, respectively with ratios (molar)1/1/8/16, with a space velocity of 950 Nl./l./hr. One obtainsconversions:

Percent Into acrylanitrile 70.4 Into acetonitrile 2.5 Into hydrocyanicacid 6.3

With a yield of useful product of 85.6%.

EXAMPLE 3 Over the catalyst of Example 2 a mixture of butene-2, ammonia,air and water in a molar ratio, respectively, of 1/1/6/20 is passed at avelocity of about 1000 Nl./l./hr., While varying the temperature,obtaining the results tabu- Under the same conditions of Example 3butene-l is used instead of butene-2, obtaining the results of thefollowing table:

Conversion, percent Temperature Yield of use- O. in] prod.,

Acrylonitrile Acetonitrile HON percent EXAMPLE 5 The synthesis ofacrylonitrile is carried out on the catalyst of Example 2, from ammonia,air and a refinery gas having the following composition:

Percent molar c rr crr 1.3 0,11 17.5 C3H8 21.1 iso-C 11 c u 8.2 04H,33.3

The volumetric ratios in the feed between refinery gas, ammonia, air andwater are 1/ 1/ 3.5/20.

41 Operating at a space velocity of 983 Nl./1/hr., at 515 C., thefollowing molar conversions with respect to the unsaturated C and Ccompounds are obtained:

Percent Conversion into acrylonitrile 48.5 Concersion into acetonitrile14.2 Conversion into hydrocyanic acid 20.8

The yield of useful products is 79% (again calculated with respect tothe unsaturated compounds).

EXAMPLE 6 Under identical conditions as Example 5, there is effected thesynthesis of acrylonitrile from ammonia, air, water and a refinery gashaving the following composition:

Percent molar The following molar conversions with respect to theunsaturated C and 0., compounds are obtained:

Percent Conversion into acrylonitrile 4.35 Conversion into acetonitrile15.6 Conversion into hydrocyanic acid 15.8 Yield of useful products 86EXAMPLE 7 The synthesis of acrylonitrile is eifected under the sameconditions as in Example 5, feeding a refinery gas diluted inunsaturated products. The analysis of said gas is as follows:

Percent molar c rn+c r1 3.7 c n, 11.8 c n 28.9 iso-C H C4H8 15.2 C4H1027.9

The conversions with respect to the unsaturated C and C compounds are:

Percent Conversion into acrylonitrile 42.3 Conversion into acetonitrile15.9 Conversion into hydrocyanic acid 14.2 Yield of useful products Theembodiments of the invention in which an exizlusive property orprivilege is claimed are defined as folows:

1. A process for the production of acrylonitrile in which a refinery gasconsisting essentially of C H +C H in a molar ratio range of 0.6% to3.7%, of C H in a molar ratio range of 11.8% to 22.1%, of C H in a molarrange of 19.2% to 28.9%, of iso C H in a molar range of 12.5% to 18.6%,of C H in a molar ratio range of 8.2% to 20.1% and of C H in a molarratio range of 22.7% to 33.3%, the sum total of said components in thegas being essentially is reacted with ammonia and oxygen in the presenceof an oxidation catalyst consisting essentially of a mixture of bismuthoxide, molybdenum oxide, and vanadium oxide, where the vanadium contentis between 0.5 and 3%, the reaction being conducted at a temperaturebetween 450 C. and 525 C. and for from 0.5 to 30 seconds.

2. A process for making acrylonitrile as claimed in claim 1, wherein thetotal molar quantities of the olefins is less than the molar quantity ofthe oxygen used in the reaction.

3. A process for making acrylonitrile as claimed in claim 1, wherein thetotal molar quantities of the olefins are no greater than the molarquantity of ammonia used in the reaction.

4. A process for making acrylonitrile as claimed in claim 1, wherein thereaction is carried out in the gaseous phase in the presence of Water.

5. A process for making acrylonitrile as claimed in claim 1, wherein thereaction time is less than ten seconds.

References Cited by the Examiner UNITED STATES PATENTS Derwent, BelgiumR 6 Minekawa et a1. 260-4563 McDaniel et a1. 260-4563 X Callahan et a1.260-456. X Giordano et a1. 260-4563 Yasuhara et al 260-4563 OTHERREFERENCES eport No. 66A, p. A23, July 15,

CHARLES B. PARKER, Primary Examiner.

JOSEPH P. BRUST, Examiner.

1. A PROCESS FOR THE PRODUCTION OF ACRYLONITRILE IN WHICH A REFINERY GASCONSISTING ESSENTIALLY OF C2H4+C2H6 IN A MOLAR RATIO RANGE OF 0.6% TO3.7%, OF C3H6 IN A MOLAR RATIO RANGE OF 11.8% TO 22.1%, OF C3H8 IN AMOLAR RANGE OF 19.2% TO 28.9%, OF ISO C4H8 IN A MOLAR RANGE OF 12.5% TO18.6%, OF C4H8 IN A MOLAR RATIO RANGE OF 8.2% TO 20.1% AND OF C4H10 IN AMOLAR RATIO RANGE OF 22.7% TO 33.3%, THE SUM TOTAL OF SAID COMPONENTS INTHE GAS BEING ESSENTIALLY 100%, IS REACTED WITH AMMONIA AND OXYGEN INTHE PRESENCE OF AN OXIDATION CATALYST COSISTING ESSENTIALLY OF A MIXTUREOF ISMUTH OXIDE, MOLYBDENUM OXIDE, AND VANADIUM OXIDE, WHERE THEVANADIUM CONTENT IS BETWEEN 3.5 AND 3%, THE REACTION BEING CONDUCTED ATA TEMPERATURE BETWEEN 450%C. AND 525%C. AND FOR FROM 0.5 TO 30 SECONDS.